In an attempt to facilitate fitting of such metal clips, our British Patent No. 1555767 proposed that the clips be connected leg to leg by bridge pieces, so that several clips can be pushed up at once and progressively hammered onto the lidded can: However, these collective clips never became popular.
An overcap of plastics material is also known which comprises a planar cover disc which spans the whole lid/ring and is held onto the can by a crimped-on skirt depending from the cover disc and hooked under the double seam. However, a considerable quantity of plastics material is required to span the whole lid and ring of larger paint tins such as the 2.5 and 5 liter sizes and any yielding of the planar disc may permit the lid to yield during abuse of the container.
British Patent Application Published No. 2096107 (Nacanco) describes a clip for holding a plug lid in the ring of a paint tin. The clip has as essential features an outer member arranged to resiliently engage with the underside of the double seam, a second intermediate member arranged to resiliently engage an inner surface of the ring and/or an outer surface of the periphery of the lid, and a third, inner member arranged to engage the plug wall of the lid. It is mentioned that the clip may be made in the form of a ring of resilient plastics material. Such a notional ring will be liable to be difficult to remove from the tin once it is snap fitted into the locking position on a tin.
European Patent Application Published No. 0246 783 (Francis Packaging) describes a removable device for retaining a plug lid in a ring attached to a container body by a double seam. In one embodiment the device is an annular moulding of plastics material having a "U" shaped cross section the innermost limb of which fits inside the plug lid and the outermost limb being in the form of a plurality of inwardly barbed fingers equispaced around the device. The barbed fingers are shaped to snap fit under the double seam of a container body to hold the device firmly on the lid. If a flexible plastics material is used to achieve moulded fingers that are easy to fit, the device may not be secure. If a stiffer plastics material is used such as nylon the device may be very difficult to remove, and if less stiff material is used, the fingers may provide inadequate grip on the seam and inadequate cushioning against abuse.